I rarely encounter such problem since I'm more of an 1x1 than a large group roleplayer, but here's my two-cents:

RPing isn't like writing fanfictions or original novels/shorts where you're in full control of the whole story and all the characters - most importantly, writing to yourself - but you are sharing the control of the story with the other players equally, in terms of the main character role. It is frustrating when you encounter those who join a RP but showing signs of ignorance, and often this snowballs into cases where it can mess up the rhythm of the whole game due to conflicting events introduced by such players.

So, if you don't like to read posts by the rest of the players, then don't roleplay with other people, period. RP is not a solo game.

On the other side, if you wish people to read your posts, then you have to put in effort to make people read it. Let me ask: how do you feel reading a long post full of typo/spelling mistakes, grammatical errors, awkward sentence structures, and my greatest pet peeve of all, horrible paragraphing just to make your posts look beefy? It's even more irritating when you're expected to response to such a crappy post ASAP. You're making the other players doing the job you should have done before hitting the 'Post Reply' button.

Proofreading.

No one wants to be a Grammar (or Language as a whole) Nazi, but that doesn't mean you can be lazy about making your posts easier for the others to read - and whether English is your native tongue or not shouldn't be an excuse (English is not my first language, [s]but you can't tell until I explicitly tell you this, right?[/s]). In the beginning people can be lenient, but as the game continues you can't expect others to keep giving in the whole time. Don't blame others for not bothering to read your posts because you are the one who drove them away with your horrendous writing. Don't waste people's time deciphering your gibberish when that can be spent more fruitfully to keep the RP going forward.

To conclude my rant, reading the posts of others and proofreading your posts to make it easier for the others to read go hand in hand. Just like how in a RP you need to communicate with the other players in OOC, in IC this is how you can hold on to that connection.